(a) Field of the Invention
The present invention relates to a system and method for determining when an engine has abnormally been stopped in a hybrid electric vehicle. More particularly, the present invention relates to a system and method for determining when an engine has been abnormally a hybrid electric vehicle depending upon whether the engine of the hybrid electric vehicle is operating in a normal state or not.
(b) Description of the Related Art
Generally, in a typical internal combustion engine vehicle, the engine of the vehicle does not typical stop and restart. Thus, when the engine does stop, it is unusual. In this case, the system must control the air/fuel ratio in a different way in order to improve the engine's ability to be restarted and to reduce exhaust gas emissions.
On the other hand, in a hybrid electric vehicle the engine is frequently stopped and restarted even in a normal state based upon whether the vehicle is in an idle stop mode, an electric vehicle (EV) driving mode, or a passive run mode. These various modes help to improve the fuel efficiency of the vehicle. As a result, hybrid electric vehicles need to have an additional algorithm for distinguishing between when the engine has been stopped normally and when the engine has been stopped abnormally.
An abnormal engine stop may occur because of a breakdown of a system, a fuel blockage, misfiring, or due to the amount of air supplied to the engine, for example. In most cases, a self-diagnostic algorithm provides breakdown information and countermeasures with respect to the abnormal engine stop. It is difficult, however, to identify an occasional blockage in a fuel line or a contact failure of electric/signal system which cause the engine to stop abnormally using a self-diagnostic algorithm. In fact, a conventional hybrid electric vehicle cannot always confirm whether or not the engine has been stopped abnormally or not since the boundary between a normal stop and an abnormal engine stop is so vague.
Additionally, although hybrid electric vehicles can operate normally using only an alternative energy source (e.g., a motor and a battery) which assist the main energy source (e.g., the engine) when the abnormal engine stop occurs, the alternative energy source is not infinite, and the conventional art may not be able to identify until it is too late that the engine was previously stopped abnormally. As a result, the hybrid electric vehicle may break down eventually and have to be towed when all the alternative energy sources have been used up.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.